CN114698136A

CN114698136A - Method for performing uplink channel access in wireless communication system and apparatus therefor

Info

Publication number: CN114698136A
Application number: CN202210317482.8A
Authority: CN
Inventors: 卢珉锡; 郭真三; 孙周亨
Original assignee: Wilus Institute of Standards and Technology Inc
Current assignee: Wilus Institute of Standards and Technology Inc
Priority date: 2016-03-23
Filing date: 2017-03-22
Publication date: 2022-07-01
Also published as: KR20220092643A; US11330609B2; WO2017164647A1; US10757717B2; EP3435725A4; CN114698137A; EP3435725B1; KR102285189B1; KR102413222B1; US20190037582A1; US20220225350A1; KR20210095742A; PL3435725T3; KR20230145247A; US20230388067A1; ES2951183T3; CN108886818A; KR20230054758A; KR102586587B1; CN114698135A

Abstract

The present invention relates to a method of performing uplink channel access in a wireless communication system and an apparatus therefor. In particular, the invention comprises the following steps: receiving an uplink grant from a base station that schedules an uplink transmission in at least one subframe; and performing uplink transmission in the at least one subframe by using at least one of the first type channel access and/or the second type channel access. Performing uplink transmission by using the second type channel access when all of the at least one subframe is included in a predetermined interval determined based on downlink transmission from the base station through the unlicensed cell.

Description

Method for performing uplink channel access in wireless communication system and apparatus therefor

The application is a divisional application of a patent application with the application number 201780018454.3(PCT/KR2017/003084) which is filed in the Chinese patent office on the international application date of 2017, 03 and 22 in 19/09 in 2018 and is named as a method for accessing an unlicensed uplink channel in a wireless communication system and a device thereof.

Technical Field

The present invention relates to a wireless communication system. In particular, the present invention relates to a method and apparatus for accessing an uplink channel in an unlicensed band in a wireless communication system.

Background

In recent years, as mobile services have exploded due to the popularity of smart devices, it has been difficult to handle the increased data usage for providing cellular communication services only through the conventional licensed spectrum or LTE licensed bands.

In this case, a scheme of providing a cellular communication service using an unlicensed (alternatively, unlicensed, or unnecessary licensed) spectrum or an LTE unlicensed frequency band (e.g., 2.4GHz band, 5GHz band, etc.) has been designed as a solution to the spectrum shortage problem.

However, unlike the authorized band in which the communication service provider ensures the exclusive frequency use right through a process in the unauthorized band (such as auction, etc.), when only the adjacent band protection rule of the predetermined level is complied with, a plurality of communication facilities can be used simultaneously without limitation. Therefore, when the unlicensed band is used in the cellular communication service, it is difficult to secure a level of communication quality provided in the licensed band, and an interference problem may occur with respect to a common wireless communication device (e.g., a wireless LAN device) using the unlicensed band.

Therefore, research on a coexistence scheme with respect to a conventional unlicensed band device and a scheme for efficiently sharing a radio channel needs to be preferentially conducted in order to solve the LTE technology in the unlicensed band. That is, it is necessary to develop a Robust Coexistence Mechanism (RCM) to prevent a device using LTE technology in an unlicensed band from affecting a conventional unlicensed band device.

Disclosure of Invention

Technical problem

The present invention has been made in an effort to provide a method for efficiently transmitting a signal in a wireless communication system, and particularly, a cellular wireless communication system and an apparatus thereof. Further, the present invention has been made in an effort to provide a method for efficiently transmitting signals in a specific frequency band (e.g., an unlicensed band) and a device thereof.

The technical objects desired to be achieved in the present invention are not limited to the aforementioned objects, and other technical objects not described above will be clearly understood by those skilled in the art from the following disclosure.

Technical scheme

According to an aspect of the present invention, there is provided a method for a user equipment to perform uplink transmission to a base station through an unlicensed cell in a wireless communication system, the method including: receiving an uplink grant from a base station that schedules an uplink transmission in at least one subframe; and performing uplink transmission in the at least one subframe by using at least one of the first type of channel access or the second type of channel access. Performing uplink transmission by using the second type channel access when all of the at least one subframe is included in a predetermined interval determined based on downlink transmission from the base station through the unlicensed cell.

Further, according to an aspect of the present invention, there is provided a user equipment of a wireless communication system, the user equipment including: a wireless communication module; and a processor configured to receive an uplink grant from the base station scheduling uplink transmission in at least one subframe, and perform the uplink transmission in the at least one subframe by using at least one of the first type channel access or the second type channel access. The processor is configured to: performing uplink transmission by using the second type channel access when all of the at least one subframe is included in a predetermined interval determined based on downlink transmission from the base station through the unlicensed cell.

Preferably, the uplink grant may indicate a channel access type to be used in uplink transmission among the first type channel access or the second type channel access. Preferably, when the at least one subframe is not included in the predetermined interval or only a portion of the at least one subframe is included in the predetermined interval, the uplink transmission may be performed by using a type of channel access indicated in the uplink grant.

On the other hand, the predetermined interval may be determined based on a maximum channel occupying time set through downlink transmission, and information on whether at least one subframe is a last subframe for uplink transmission may be received through a common control channel.

In addition, when uplink transmission is performed in a next subframe of downlink transmission in the unlicensed cell, uplink transmission may be performed by using the second type channel access.

In another aspect, according to another aspect of the present invention, there is provided a method for a base station to receive an uplink transmission from a user equipment through an unlicensed cell in a wireless communication system, the method including: scheduling transmission of uplink signals in at least one subframe and transmitting an uplink grant to the user equipment indicating a channel access type to be used by the user equipment when transmitting uplink signals in the first type channel access or the second type channel access; and receiving an uplink signal in at least one subframe. The method further comprises the following steps: transmitting common downlink control information indicating that second-type channel access is performed in uplink transmission when all of the at least one subframe is included in a predetermined interval determined based on downlink transmission through the unlicensed cell.

In addition, according to another aspect of the present invention, there is provided a base station in a wireless communication system, the base station including: a wireless communication module; and a processor configured to schedule transmission of an uplink signal through the unlicensed cell in at least one subframe, transmit an uplink grant indicating a channel access type to be used when the user equipment transmits the uplink signal among the first type channel access or the second type channel access to the user equipment, and receive the uplink signal from the user equipment in the at least one subframe, and when all of the at least one subframe is included in a predetermined interval determined based on downlink transmission through the unlicensed cell, transmit common downlink control information indicating that the second type channel access is performed in the uplink transmission.

Further, the uplink grant may indicate the first type channel access when the at least one subframe is not included in the predetermined interval or only a portion of the at least one subframe is included in the predetermined interval. In addition, the common downlink control information may include information on whether at least one subframe is a last subframe for uplink transmission.

Advantageous effects

According to an exemplary embodiment of the present invention, a method for efficiently transmitting a signal in a wireless communication system, particularly, a cellular wireless communication system and an apparatus thereof, is provided. Further, a method for efficiently accessing a channel in a specific frequency band (e.g., an unlicensed band) and an apparatus thereof are provided.

The effects obtained in the present invention are not limited to the aforementioned effects, and other effects not described above will be clearly understood by those skilled in the art from the following disclosure.

Drawings

The accompanying drawings, which are included to provide a part of the detailed description, provide embodiments of the present invention and together with the detailed description, explain technical problems of the present invention.

Fig. 1 illustrates physical channels used in a third generation partnership project (3GPP) system and a general signal transmission method using the physical channels.

Fig. 2 illustrates one example of a radio frame structure used in a wireless communication system.

Fig. 3 illustrates one example of a Downlink (DL)/Uplink (UL) slot structure used in a wireless communication system.

Fig. 4 illustrates a structure of a downlink Subframe (SF).

Fig. 5 illustrates a structure of an uplink subframe.

Fig. 6 is a schematic diagram for describing single carrier communication and multicarrier communication.

Fig. 7 illustrates an example of applying a cross-carrier scheduling technique.

Fig. 8 illustrates an ACK/NACK (a/N) transmission procedure in case of a single cell.

Fig. 9 illustrates an authorized assisted access (LAA) service environment.

Fig. 10 illustrates a deployment scenario of user equipment and base stations in an LAA service environment.

Fig. 11 illustrates a communication scheme (e.g., wireless LAN) operating in an unlicensed band in the related art.

Fig. 12 to 13 illustrate a Listen Before Talk (LBT) procedure for downlink transmission.

Fig. 14 illustrates downlink transmission in the unlicensed band.

Fig. 15 is a diagram illustrating a case where a PDCCH including only an uplink grant is transmitted without PDSCH transmission as an embodiment of the present invention.

Fig. 16 is a schematic diagram illustrating a case where an EPDCCH including only an uplink grant is transmitted without PDSCH transmission as an embodiment of the present invention.

Fig. 17 is a diagram illustrating a case where LBT is independently performed for a subframe for transmitting only a UL grant without PDSCH transmission and a subframe(s) for performing PDSCH transmission according to an embodiment of the present invention.

Fig. 18 is a diagram illustrating a case where LBT is independently performed for a subframe for transmitting only a UL grant without PDSCH transmission and a subframe(s) for performing PDSCH transmission according to an embodiment of the present invention.

Fig. 19 is a diagram illustrating an example of a handover LBT type when DL scheduling occurs between UL grant transmission and corresponding UL traffic transmission according to an embodiment of the present invention.

Fig. 20 is a diagram illustrating another example of a handover LBT type according to an embodiment of the present invention when DL scheduling occurs between UL grant transmission and corresponding UL traffic transmission.

Fig. 21 is a diagram illustrating another example of a handover LBT type according to an embodiment of the present invention when DL scheduling occurs between UL grant transmission and corresponding UL traffic transmission.

Fig. 22 is a diagram illustrating a method of performing UL channel access for continuous UL transmission after DL transmission in an LAA cell.

Fig. 23 shows an example in which a terminal transmits a data channel to a base station according to another embodiment of the present invention.

Fig. 24 illustrates a configuration of a user equipment and a base station according to an embodiment of the present invention.

Detailed Description

Terms used in the present specification adopt general terms that are widely used at present as much as possible by considering functions in the present invention, but may be changed according to intentions, custom, and the emergence of new technology of those skilled in the art. Further, in a specific case, there are terms arbitrarily selected by the applicant, and in this case, their meanings will be described in corresponding description parts of the present invention. Accordingly, the present invention is intended to indicate that the terms used in the present specification should be analyzed not only based on the names of the terms but also based on the substantial meanings of the terms and contents throughout the present specification.

Throughout this specification and the claims that follow, when an element is described as being "coupled" to another element, it may be "directly coupled" to the other element or "electrically coupled" to the other element by a third element. Further, unless explicitly described to the contrary, the words "comprise" and variations such as "comprises" or "comprising" will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. Also, in some exemplary embodiments, the limit may be replaced with "greater than" or "less than", respectively, as appropriate, such as "equal to or greater than" or "equal to or less than" based on a particular threshold.

Techniques such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), single carrier FDMA (SC-FDMA), etc., may be used in various wireless access systems. CDMA may be implemented through radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA 2000. TDMA can be implemented by a radio technology such as global system for mobile communications (GSM)/General Packet Radio Service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented through radio technologies such as IEEE 802.11(Wi-Fi), IEEE802.16(WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), etc. UTRA is part of the Universal Mobile Telecommunications System (UMTS). Third generation partnership project (3GPP) Long Term Evolution (LTE) is part of evolved UMTS (E-UMTS) using evolved UMTS terrestrial radio access (E-UTRA), and LTE-advanced (a) is an evolved version of 3GPP LTE. The 3GPP LTE/LTE-a is described mainly for clarity of description, but the technical spirit of the present invention is not limited thereto.

Fig. 1 illustrates physical channels used in a 3GPP system and a general signal transmission method using the physical channels. The user equipment receives information from the base station through a Downlink (DL), and the user equipment transmits information to the base station through an Uplink (UL). Information transmitted/received between the base station and the user equipment includes data and various control information, and various physical channels exist according to the type/purpose of the information transmitted/received between the base station and the user equipment.

When the power of the user equipment is turned on or the user equipment enters a cell in a new manner, the user equipment performs an initial cell search operation including synchronization with a base station, etc. (S301). To this end, the user equipment receives a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) from the base station to synchronize with the base station and obtain information including a cell ID and the like. Thereafter, the user equipment receives a physical broadcast channel from the base station to obtain the intra-cell broadcast information. The user equipment receives a downlink reference signal (DL RS) to verify a downlink channel state in an initial cell search step.

The user equipment that completes the initial cell search receives a Physical Downlink Control Channel (PDCCH) and a Physical Downlink Shared Channel (PDSCH) according to information loaded on the PDCCH to obtain more detailed system information (S302).

When there is no radio resource for initial access to the base station or signal transmission, the user equipment may perform a random access procedure (RACH procedure) for the base station (S303 to S306). To this end, the user equipment may transmit a preamble through a Physical Random Access Channel (PRACH) (S303), and receive a response message for the preamble through a PDCCH and a PDSCH corresponding thereto (S304). In case of contention-based RACH, a contention resolution procedure may also be performed.

Thereafter, the user equipment may receive the PDCCH/PDSCH (S307) and transmit a Physical Uplink Shared Channel (PUSCH)/Physical Uplink Control Channel (PUCCH) (S308) as a general procedure. The user equipment receives Downlink Control Information (DCI) through the PDCCH. The DCI includes control information (such as resource allocation information) for the user equipment, and the format varies according to the purpose of use. Control information transmitted by the user equipment to the base station is designated as Uplink Control Information (UCI). The UCI includes acknowledgement/negative acknowledgement (ACK/NACK), Channel Quality Indicator (CQI), Precoding Matrix Index (PMI), Rank Indicator (RI), and the like. UCI may be transmitted through PUSCH and/or PUCCH.

Fig. 2 illustrates one example of a radio frame structure used in a wireless communication system. Fig. 2 (a) illustrates a frame structure for Frequency Division Duplexing (FDD), and fig. 2 (b) illustrates a frame structure for Time Division Duplexing (TDD).

Referring to fig. 2, the frame structure may have a length of 10ms (307200Ts) and may be composed of 10 Subframes (SF). Ts denotes the sampling time and is denoted as Ts ═ 1/(2048 × 15 kHz). Each subframe may have a length of 1ms and may consist of 2 slots. Each slot has a length of 0.5 ms. A time for transmitting one subframe is defined as a Transmission Time Interval (TTI). The time resources may be distinguished by radio frame number/index, subframe number/index #0 to #9, and slot number/index #0 to # 19.

The radio frame may be configured differently according to the duplex mode. In the FDD mode, downlink transmission and uplink transmission are distinguished by frequency, and a radio frame includes only one of a downlink subframe and an uplink subframe for a specific frequency band. In the TDD mode, downlink transmission and uplink transmission are distinguished by time, and a radio frame includes both of a downlink subframe and an uplink subframe for a specific frequency band.

Fig. 3 illustrates a structure of a downlink/uplink slot.

Referring to fig. 3, a slot includes a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols in a time domain and a plurality of Resource Blocks (RBs) in a frequency domain. An OFDM symbol also means one symbol period. According to the multiple access scheme, the OFDM symbol may be referred to as an OFDMA symbol, a single-carrier frequency division multiple access (SC-FDMA) symbol, or the like. The number of OFDM symbols included in one slot may be variously modified according to the length of a Cyclic Prefix (CP). For example, in the case of the normal CP, one slot includes 7 OFDM symbols, and in the case of the extended CP, one slot includes 6 OFDM symbols. Define RB as N in the time domain^DL/UL _symb(e.g., 7) consecutive OFDM symbols and N in the frequency domain^RB _sc(e.g., 12) consecutive subcarriers. A resource composed of one OFDM symbol and one subcarrier is referred to as a Resource Element (RE) or tone. One RB is formed by N^DL/UL _symb*N^RB _scAnd (4) resource element composition.

The resources of a slot may be represented by N^DL/UL _RB*N^RB _scSubcarrier and N^DL/UL _symbA resource grid of OFDM symbols. Each RE in the resource grid is uniquely defined by an index pair (k,1) of each timing. K denotes the number from 0 to N in the frequency domain^DL/UL _RB*N^RB _sc-1 an index given, and 1 denotes a number from 0 to N in the time domain^DL/UL _symb1 a given index. Here, N^DL _RBRepresents the number of Resource Blocks (RBs) in a downlink slot, and N^UL _RBIndicating the number of RBs in the UL slot. N is a radical of^DL _RBAnd N^UL _RBDepending on the DL transmission bandwidth and the UL transmission bandwidth, respectively. N is a radical of^DL _symbRepresents the number of symbols in a downlink slot, and N^UL _symbIndicating the number of symbols in the UL slot. N is a radical of^RB _scIndicating the number of subcarriers constituting one RB. One resource grid is set for each antenna port.

Fig. 4 illustrates a structure of a downlink subframe.

Referring to fig. 4, a subframe may be composed of 14 OFDM symbols. According to the subframe setting, the first 1 to 3 (alternatively, 2 to 4) OFDM symbols are used as a control region, and the remaining 13 to 11 (alternatively, 12 to 10) OFDM symbols are used as a data region. R1 to R4 represent reference signals for antenna ports 0 to 3. The control channels allocated to the control region include a Physical Control Format Indicator Channel (PCFICH), a physical hybrid ARQ indicator channel (PHICH), a Physical Downlink Control Channel (PDCCH), and the like. The data channel allocated to the data region includes a PDSCH and the like. When Enhanced Pdcch (EPDCCH) is set, PDSCH and EPDCCH are multiplexed by Frequency Division Multiplexing (FDM) in the data region.

A PDCCH, which is a physical downlink control channel, is allocated to the first n OFDM symbols of the subframe, and n, which is an integer of 1 (alternatively, 2) or more, is represented by PCFICH. The PDCCH announces information associated with resource allocation of a Paging Channel (PCH) and a downlink shared channel (DL-SCH) as transport channels, uplink scheduling grants, HARQ information, and the like to each user equipment or user equipment group. Data (i.e., transport blocks) of the PCH and DL-SCH are transmitted through the PDSCH. Each of the base station and the user equipment generally transmits and receives data through the PDSCH except for specific control information or specific service data.

Information indicating to which user equipment (one or more user equipments) data of the PDSCH is transmitted, information indicating how the user equipment receives and decodes the PDSCH data, etc. are transmitted while being included in the PDCCH/EPDCCH. For example, it is assumed that the PDCCH/EPDCCH is CRC-masked with a Radio Network Temporary Identity (RNTI) called "a" and information on data transmitted by using a radio resource (e.g., frequency location) called "B" and a DCI format called "C", that is, transmission format information (e.g., a transport block size, a modulation scheme, coding information, etc.) is transmitted through a specific subframe. In this case, the user equipments in the cell monitor the PDCCH/EPDCCH by using their RNTI information, and when one or more user equipments having the "a" RNTI are provided, the user equipments receive the PDCCH/EPDCCH and receive the PDSCH denoted by "B" and "C" through information on the received PDCCH/EPDCCH.

Fig. 5 illustrates a structure of an uplink subframe.

Referring to fig. 5, a subframe may be divided into a control region and a data region in a frequency domain. PUCCH is allocated to the control region and carries UCI. The PUSCH is allocated to the data region and carries user data.

The following control information may be transmitted using PUCCH.

-Scheduling Request (SR): information for requesting UL-SCH resources. The SR is transmitted by using an on-off keying (OOK) scheme.

-HARQ-ACK: a response to the PDCCH and/or a response to a downlink data packet (e.g., codeword) on the PDSCH. The codeword is the coding format of the transport block. The HARQ-ACK indicates whether the PDCCH and the PDSCH are successfully received. The HARQ-ACK response includes positive ACK (simply ACK), Negative ACK (NACK), Discontinuous Transmission (DTX), or NACK/DTX. DTX denotes a case where the user equipment loses PDCCH (alternatively, semi-persistent scheduling (SPS) PDSCH) and NACK/DTX refers to NACK or DTX. HARQ-ACK is used in combination with HARQ-ACK/NACK and ACK/NACK.

-Channel State Information (CSI): feedback information on a downlink channel. The feedback information related to Multiple Input Multiple Output (MIMO) includes RI and PMI.

Hereinafter, carrier aggregation will be described. Carrier aggregation means a method in which a wireless communication system uses a plurality of frequency blocks as one large logical frequency band in order to use a wider frequency band. When the entire system band is extended by carrier aggregation, a frequency band for communication with each user equipment is defined by a Component Carrier (CC) unit.

Fig. 6 is a schematic diagram for describing single carrier communication and multicarrier communication. Fig. 6 (a) illustrates a subframe structure of a single carrier, and fig. 6 (b) illustrates a subframe structure of a multi-carrier of carrier aggregation.

Fig. 6 (b) illustrates a subframe structure of a multicarrier for carrier aggregation.

Referring to fig. 6 (a), in a single carrier system, a base station and a user equipment perform data communication through one DL band and one UL band corresponding thereto. The DL/UL band is divided into a plurality of orthogonal subcarriers, and each band operates at one carrier frequency. In FDD, DL and UL bands operate at different carrier frequencies, respectively, and in TDD, DL and UL bands operate at the same carrier frequency. The carrier frequency refers to the center frequency of the band.

Referring to fig. 6 (b), carrier aggregation is distinguished from an OFDM system that performs DL/UL communication in a base band divided into a plurality of subcarriers by using one carrier frequency, because carrier aggregation performs DL/UL communication by using a plurality of carrier frequencies. Referring to (b) of fig. 6, three 20MHz CCs are aggregated in each of UL and DL to support a bandwidth of 60 MHz. The CCs may or may not be adjacent to each other in the frequency domain. For convenience sake, fig. 6 (b) illustrates a case where the bandwidth of the UL CC and the bandwidth of the DL CC are identical to and symmetrical to each other, but the bandwidths of the respective CCs may be independently decided. Further, asymmetric carrier aggregation in which the number of UL CCs and the number of DL CCs are different from each other is also available. DL/UL CC(s) are independently allocated/configured for each user equipment, and the DL/UL CC(s) allocated/configured for the user equipment are designated as serving UL/DL CC(s) of the corresponding user equipment.

The base station may enable some or all of the serving CCs or disable some CCs of the user equipment. When the base station allocates the CC(s) to the user equipment, if the CC allocation to the user equipment is completely reconfigured or if the user equipment is not handed over, at least one specific CC among the CC(s) configured for the corresponding user equipment is not disabled. A specific CC that is always activated is referred to as a primary CC (pcc), and a CC that a base station can be arbitrarily activated/deactivated is referred to as a secondary CC (scc). The PCC and SCC may be distinguished based on the control information. For example, specific control information may be set to be transmitted/received only through a specific CC, and the specific CC may be referred to as a PCC, and the remaining CC(s) may be referred to as SCC(s). PUCCH is transmitted only on PCC.

In 3GPP, the concept of a cell is used to manage radio resources. A cell is defined as a combination of DL resources and UL resources, i.e., a combination of DL CC and UL CC. The cell may be configured by only DL resources or a combination of DL resources and DL resources. When carrier aggregation is supported, a linkage between carrier frequencies of DL resources (alternatively, DL CCs) and carrier frequencies of UL resources (alternatively, UL CCs) may be indicated with system information. For example, the combination of DL resources and UL resources may be indicated with system information block type 2(SIB2) linkage. The carrier frequency refers to a center frequency of each cell or CC. A cell corresponding to the PCC is referred to as a primary cell (PCell), and a cell corresponding to the SCC is referred to as a secondary cell (SCell). The carrier corresponding to the PCell is a DL PCC in the downlink, and the carrier corresponding to the PCell is an UL PCC in the uplink. Similarly, the carrier corresponding to the SCell is a DL SCC in downlink, and the carrier corresponding to the SCell is an UL SCC in uplink. The serving cell(s) may be composed of a PCell and 0 or more scells, depending on user equipment capabilities. For a user equipment in RRC _ CONNECTED state but without any configuration of carrier aggregation or not supporting carrier aggregation, there is only one serving cell consisting of only PCell.

Fig. 7 illustrates an example of applying cross-carrier scheduling. When cross-carrier scheduling is configured, a control channel transmitted through the first CC may schedule a data channel transmitted through the first CC or the second CC by using a Carrier Indicator Field (CIF). The CIF is included in the DCI. In other words, the scheduling cell is configured, and the DL grant/UL grant transmitted in the PDCCH region of the scheduling cell schedules the PDSCH/PUSCH of the scheduled cell. That is, the search spaces of the plurality of component carriers exist in the PDCCH region of the scheduling cell. The PCell may be basically a scheduling cell, and a specific SCell may be designated as the scheduling cell by an upper layer.

In fig. 7, it is assumed that three DL CCs are aggregated. Herein, DL component carrier #0 is assumed to be DL PCC (alternatively, PCell), and DL component carrier #1 and DL component carrier #2 are assumed to be DL SCC (alternatively, SCell). Further, it is assumed that DL PCC is set to monitor PDCCH of CC. When CIF is disabled, the corresponding DL CC may transmit only PDCCH scheduling its PDSCH without CIF according to LTE PDCCH rules (non-cross-carrier scheduling and self-carrier scheduling). In contrast, when CIF is enabled by UL-specific (alternatively, UL group-specific or cell-specific) upper layer signaling, a specific CC (e.g., DL PCC) may transmit a PDCCH scheduling a PDSCH of DL CC a and a PDCCH scheduling a PDSCH of another CC by using CIF (cross-carrier scheduling). In contrast, in another DL CC, a PDCCH is not transmitted.

Fig. 8 illustrates an ACK/NACK (a/N) transmission procedure in case of a single cell. (i) PDSCH scheduled by PDCCH, (ii) PDSCH without corresponding PDCCH (i.e., SPS PDSCH), and (iii) PDCCH indicating SPS release. The figure illustrates a process of transmitting ACK/NACK for PDSCH of (i). The PDCCH includes EPDCCH.

Referring to fig. 8, a user equipment receives a PDCCH (or EPDCCH) in a subframe # n-k (S802), and receives a PDSCH indicated by the PDCCH (S804) in the same subframe, PDCCH transmission scheduling information (i.e., DL grant), and the PDSCH transmits one or more (e.g., two) transport blocks TB (or codewords CW) according to a transmission mode. Thereafter, the user equipment may transmit ACK/NACK for the PDSCH (i.e., transport block) in subframe # n (S806). One bit of ACK/NACK may be transmitted in response to a single transport block, and two bits of ACK/NACK may be transmitted in response to two transport blocks. The ACK/NACK is basically transmitted via the PUCCH, but when there is PUSCH transmission in subframe # n, the ACK/NACK is transmitted via the PUSCH. k denotes a time interval between a DL subframe and a UL subframe. In FDD, K is 4, and K in TDD may be given by a Downlink Association Set Index (DASI). ACK/NACK means HARQ-ACK. The HARQ-ACK response includes ACK, NACK, DTX, and NACK/DTX.

When a plurality of cells are configured for the user equipment, the ACK/NACK information may be transmitted by using PUCCH format 3, or may be transmitted by using a channel selection scheme based on PUCCH format 1 b.

Each cell configures an ACK/NACK payload of PUCCH format 3, and the ACK/NACK payloads are concatenated according to a cell index order. The ACK/NACK payload is configured for all cells configured for the user equipment regardless of whether actual data is transmitted in each cell. Each bit in the ACK/NACK payload represents HARQ-ACK feedback for that transport block (or codeword). The HARQ-ACK feedback indicates ACK or NACK, and DTX is treated as NACK. NACK and DTX have the same HARQ-ACK feedback value. If necessary, the base station can distinguish NACK from DTX by using information on a control channel that the base station has transmitted to the user equipment.

When two cells are aggregated, a PUCCH format 1 b-based channel selection scheme may be configured for ACK/NACK transmission. In the channel selection scheme based on the PUCCH format 1b, ACK/NACK responses to a plurality of transport blocks (or codewords) are identified by combining PUCCH resource indexes and bit values.

Fig. 9 illustrates an authorized assisted access (LAA) service environment.

Referring to fig. 9, a service environment in which LTE technology (11) and LTE-unlicensed (LTE-U) in a conventional licensed band, which have been actively discussed, or LAA, which is LTE technology (12) in an unlicensed band, can be connected to each other, can be provided to a user. For example, LTE technology in the licensed band (11) and LTE technology in the unlicensed band (12) in an LAA environment may be integrated by using techniques such as carrier aggregation, which may help to extend network capacity. Further, in an asymmetric traffic structure in which the amount of downlink data is greater than the amount of uplink data, the LAA may provide an optimized LTE service according to various requirements or environments. For convenience, LTE technology in licensed (alternatively, licensed or allowed) bands is referred to as LTE licensed (LTE-L), and LTE technology in unlicensed (alternatively, unlicensed, not-licensed) bands is referred to as LTE unlicensed (LTE-U) or LAA.

Fig. 10 illustrates a layout scenario of user equipment and base stations in an LAA service environment. The frequency band for which the LAA service environment is intended has a short wireless communication reach due to high frequency characteristics. In view of this, the layout scenarios of the user equipment and the base station in an environment where the conventional LTE-L service and the LAA service coexist may be an overlay model and a co-location model.

In the overlay model, the macro base station may perform wireless communication with X UEs and X' UEs in the macro area (32) by using licensed carriers and connect with a plurality of Remote Radio Heads (RRHs) through an X2 interface. Each RRH can perform wireless communication with X UEs or X' UEs in a predetermined area (31) by using an unlicensed carrier. The frequency bands of the macro base station and the RRH are different from each other without interfering with each other, but data needs to be quickly exchanged between the macro base station and the RRH through an X2 interface in order to use the LAA service as a secondary downlink channel for the LTE-L service through carrier aggregation.

In the co-location model, the pico/femto base station may perform wireless communication with the Y UE by using a licensed carrier and an unlicensed carrier. However, the use of LTE-L services and LAA services by pico/femto base stations for downlink transmission may be limited. The coverage (33) of the LTE-L service and the coverage (34) of the LAA service may be different according to frequency band, transmission power, etc.

When LTE communication is performed in an unlicensed band, a conventional device (e.g., a wireless LAN (Wi-Fi) device) performing communication in a corresponding unlicensed band may not demodulate an LTE-U message or data and determine the LTE-U message or data as one energy for performing an interference avoidance operation through an energy detection technique. That is, when energy corresponding to the LTE-U message or data is less than-62 dBm, the wireless LAN device may perform communication by ignoring the corresponding message or data. Therefore, the user equipment performing LTE communication in the unlicensed band may be frequently interfered with by the wireless LAN device.

Therefore, a specific frequency band needs to be allocated or reserved for a specific time in order to effectively implement LTE-U technology/service. However, since a peripheral device performing communication through an unlicensed band attempts access based on an energy detection technique, there is a problem in that it is difficult to perform an efficient LTE-U service. Therefore, there is a need for a preferential study of a coexistence scheme with respect to a conventional unlicensed band device and a scheme for efficiently sharing a radio channel in order to solve the LTE-U technology. That is, it is required to develop a robust coexistence mechanism in which the LTE-U device does not affect the conventional unlicensed band device.

Fig. 11 illustrates a communication scheme (e.g., wireless LAN) operating in an unlicensed band in the related art. Since most devices operating in the unlicensed band operate based on Listen Before Talk (LBT), a Clear Channel Assessment (CCA) technique of sensing a channel before data transmission is performed.

Referring to fig. 11, a wireless LAN device (e.g., an AP or an STA) checks whether a channel is busy by performing carrier sensing before transmitting data. When a radio signal of a predetermined strength or more is sensed in a channel transmitting data, it is determined that the corresponding channel is busy, and the wireless LAN device delays access to the corresponding channel. This process is referred to as clear channel assessment and the signal level used to decide whether a signal is sensed is referred to as a CCA threshold. Meanwhile, when no radio signal is sensed in the corresponding channel or a radio signal having a strength less than the CCA threshold is sensed, it is determined that the channel is idle.

When it is determined that the channel is idle, the terminal having data to transmit performs a backoff process after a delay period (e.g., an arbitration interframe space (AIFS), PCF IFS (PIFS), etc.). The delay period refers to the minimum time that the terminal needs to wait after the channel is idle. The backoff procedure allows the terminal to stand by further for a predetermined time after the delay period. For example, during a channel is in an idle state, a terminal stands by while reducing a slot time for a slot time corresponding to a random number allocated to the terminal in a Contention Window (CW), and a terminal that completely exhausts the slot time may attempt to access a corresponding channel.

When the terminal successfully accesses the channel, the terminal may transmit data through the channel. When the data is successfully transmitted, the CW Size (CWs) is reset to the initial value (CWmin). Conversely, when data is not successfully transmitted, the CWS doubles. Therefore, the terminal is allocated with a new random number within a range twice as large as the previous random number range to perform the backoff process in the next CW. In the wireless LAN, only ACK is defined as receiving response information to data transmission. Thus, when an ACK is received for a data transmission, the CWS is reset to an initial value, and when no feedback information is received for a data transmission, the CWS is doubled.

As described above, since most of communications in the unlicensed band in the related art operate based on LBT, LTE also considers LBT in LAA to coexist with a conventional apparatus. Specifically, in LTE, channel access methods on the unlicensed band may be classified into the following 4 categories according to the presence/application scheme of LBT.

(1) Class 1: without LBT

-not performing the LBT procedure performed by the Tx entity.

(2) Class 2: LBT without random back-off

-determining a time interval during which the channel needs to be sensed in an idle state before a Tx entity performs a transmission on the channel. No random backoff is performed. This may be referred to as type 2 channel access.

(3) Class 3: LBT with random backoff of CWs of fixed size

LBT method that performs random backoff by using CW of fixed size. The Tx entity has a random number N in the CW, and the CW size is defined by a minimum/maximum value. The CW size is fixed. The random number N is used to determine the time interval in which the channel needs to be sensed in the idle state before the Tx entity performs a transmission on the channel.

(4) Class 4: LBT with random backoff of CWs of variable size

LBT method that performs random backoff by using CW of variable size. The Tx entity has a random number N in the CW, and the CW size is defined by the minimum/maximum value of N. The Tx entity may change the CW size when generating the random number N. The random number N is used to determine the time interval in which the channel needs to be sensed in the idle state before the Tx entity performs a transmission on the channel. This may be referred to as type 1 channel access.

Fig. 12 and 13 illustrate downlink transmission procedures based on class 4 LBT. Class 4LBT may be used to guarantee fair channel access with Wi-Fi. Referring to fig. 12 and 13, the LBT procedure includes an initial cca (icca) and an extended cca (ecca). In the ICCA, random backoff is not performed, and in the ECCA, random backoff is performed by using CW of variable size. The ICCA is adapted for a case where a channel is idle when signal transmission is required, and the ECCA is adapted for a case where a channel is busy when downlink transmission is performed immediately before.

Referring to fig. 12, a downlink transmission procedure based on class 4LBT, type 1 channel access may be performed as follows.

Initial CCA

-S1202: the base station verifies that the channel is idle.

-S1204: the base station verifies whether a signal transmission is required. When signal transmission is not required, the process returns to S1202, and when signal transmission is required, the process proceeds to S1206.

-S1206: the base station verifies whether the channel is idle for the ICCA delay period (BCCA). The ICCA delay period is configurable. As an implementation example, the ICCA delay period may consist of an interval of 16 μ s and n consecutive CCA slots. Herein, n may be a positive integer, and one CCA slot interval may be 9 μ s. The number of CCA slots may be configured in different ways depending on the QoS class. The ICCA delay period may be set to an appropriate value by considering the delay period of Wi-Fi (e.g., DIFS or AIFS). For example, the ICCA delay period may be 34 μ s. When the channel is idle for the ICCA delay period, the base station may perform a signal transmission procedure (S1208). When it is determined that the channel is busy during the ICCA delay period, the process proceeds to S1212 (ECCA).

-S1208: the base station may perform a signal transmission procedure. When the signal transmission is not performed, the process proceeds to S1202(ICCA), and when the signal transmission is performed, the process proceeds to S1210. Even in the case where the backoff count N reaches 0 in S1218 and S1208 is performed, when signal transmission is not performed, the procedure proceeds to S1202(ICCA), and when signal transmission is performed, the procedure proceeds to S1210.

-S1210: when no additional signaling is needed, the process proceeds to S1202(ICCA), and when additional signaling is needed, the process proceeds to S1212 (ECCA).

Extended CCA

-S1212: the base station generates a random number N in CW. N is used as a count during the backoff process and is generated from [0, q-1 ]. The CW may consist of q ECCA slots and the ECCA slot size may be 9 μ s or 10 μ s. In S1214, the CW Size (CWs) may be defined as q and may be variable. Thereafter, the base station proceeds to S1216.

-S1214: the base station may update the CWS. CWS q may be updated to a value between X and Y. The X and Y values are configurable parameters. CWS update/adjustment (dynamic backoff) may be performed each time N is generated and may be performed semi-statically within a predetermined time interval (semi-static backoff). The CWS may be updated/adjusted based on an exponential backoff or a binary backoff. That is, the CWS may be updated/adjusted in the form of a square of 2 or a multiple of 2. In conjunction with PDSCH transmission, the CWS may be updated/adjusted based on feedback/reports (e.g., HARQ ACK/NACK) of the user equipment or based on base station sensing.

-S1216: the base station verifies whether the channel is idle for an ECCA delay period (DeCCA). The ECCA delay period is configurable. As an implementation example, the ECCA delay period may consist of an interval of 16 μ s and n consecutive CCA slots. Herein, n may be a positive integer, and one CCA slot interval may be 9 μ s. The number of CCA slots may be configured in different ways depending on the QoS class. The ECCA latency period may be set to an appropriate value by considering the latency period of Wi-Fi (e.g., DIFS or AIFS). For example, the ECCA delay period may be 34 μ s. When the channel is idle for the ECCA delay period, the base station proceeds to S1218. When it is determined that the channel is busy during the ECCA delay period, the base station repeats S1216.

-S1218: the base station verifies whether N is 0. When N is 0, the base station may perform a signal transmission procedure (S1208). In this case, (N ═ 0), the base station may not immediately perform transmission, and perform a CCA check for at least one slot to continue the ECCA procedure. When N is not 0 (i.e., N >0), the process proceeds to S1220.

-S1220: the base station senses the channel during one ECCA slot interval (T). The ECCA slot size may be 9 or 10 mus and the actual sensing time may be at least 4 mus.

-S1222: when it is determined that the channel is idle, the procedure proceeds to S1224. When it is determined that the channel is busy, the process returns to S1216. That is, one ECCA delay period is applied again after the channel is idle, and N is not counted during the ECCA delay period.

-S1224: n minus 1(ECCA count down)

Fig. 13 is generally the same/similar to the transmission process of fig. 12 and differs from fig. 12 according to an embodiment. Therefore, the detailed problem can be described with reference to the contents of fig. 12.

-S1302: the base station verifies whether a signal transmission is required. When signal transmission is not required, S1302 is repeated, and when signal transmission is required, the process proceeds to S1304.

-S1304: the base station verifies whether the time slot is free. The process continues to S1306 when the slot is free, and to S1312(ECCA) when the slot is busy. The slots may correspond to CCA slots in fig. 12.

-S1306: the base station verifies whether the channel is idle for a delay period (D). D may correspond to the ICCA delay period in fig. 12. When the channel is idle for the delay period, the base station may perform a signal transmission procedure (S1308). When it is determined that the channel is busy during the delay period, the process proceeds to S1304.

-S1308: the base station may perform a signaling procedure, if desired.

-S1310: when the signal transmission is not performed, the process proceeds to S1302(ICCA), and when the signal transmission is performed, the process proceeds to S1312 (ECCA). Even in the case where the backoff count N reaches 0 in S1318 and S1308 is performed, when signal transmission is not performed, the procedure proceeds to S1302(ICCA), and when signal transmission is performed, the procedure proceeds to S1312 (ECCA).

Extended CCA

-S1312: the base station generates a random number N in CW. N is used as a count during the backoff process and is generated from [0, q-1 ]. In S1314, the CW Size (CWs) may be defined as q and may be variable. Thereafter, the base station proceeds to S1316.

-S1314: the base station may update the CWS. CWS q may be updated to a value between X and Y. The X and Y values are configurable parameters. CWS update/adjustment (dynamic backoff) may be performed each time N is generated and may be performed semi-statically within a predetermined time interval (semi-static backoff). The CWS may be updated/adjusted based on an exponential backoff or a binary backoff. That is, the CWS may be updated/adjusted in the form of a square of 2 or a multiple of 2. In conjunction with PDSCH transmission, the CWS may be updated/adjusted based on feedback/reports (e.g., HARQ ACK/NACK) of the user equipment or based on base station sensing.

-S1316: the base station verifies whether the channel is idle for a delay period (D). D may correspond to the ECCA delay period in fig. 12. D in S1306 and D in S1316 may be identical to each other. When the channel is idle for the delay period, the base station proceeds to S1318. When it is determined that the channel is busy during the delay period, the base station repeats S1316.

-S1318: the base station verifies whether N is 0. When N is 0, the base station may perform a signal transmission procedure (S1308). In this case, (N ═ 0), the base station may not immediately perform transmission, and perform a CCA check during at least one slot to continue the ECCA procedure. When N is not 0 (i.e., N >0), the process proceeds to S1320.

-S1320: the base station selects one of an operation of subtracting 1 from N and an operation of not decreasing N (self-delay). The self-delay operation may be performed according to the implementation/selection of the base station, and the base station does not perform energy detection sensing and even ECCA countdown in the self-delay.

-S1322: the base station may select one of an operation of not performing energy detection sensing and an energy detection operation. When the energy detection sensing is not performed, the process proceeds to S1324. When the energy detection operation is performed, if the energy level is equal to or less than the energy detection threshold (i.e., idle), the process proceeds to S1324. If the energy level is greater than the energy detection threshold (i.e., busy), the process returns to S1316. That is, a delay period is applied again after the channel is idle, and N is not calculated for the delay period.

-S1324: the process proceeds to S1318.

Fig. 14 illustrates an example in which a base station performs downlink transmission in an unlicensed band. The base station may aggregate cells of one or more licensed bands (for convenience, LTE-L cells) and cells of one or more unlicensed bands (for convenience, LTE-U cells). In fig. 14, a case is assumed where one LTE-L cell and one LTE-U cell are aggregated for communication with a user equipment. The LTE-L cell may be a PCell, and the LTE-U cell may be an SCell. In the LTE-L cell, the base station may use only frequency resources and perform an operation according to LTE in the related art. Accordingly, all radio frames may be composed of regular subframes (rSF) having a length of 1ms (see fig. 2), and DL transmission (e.g., PDCCH and PDSCH) may be performed in each subframe (see fig. 1). Meanwhile, in an LTE-U cell, downlink transmission is performed based on LBT for coexistence with a conventional device (e.g., a Wi-Fi device). Further, a specific frequency band needs to be allocated or reserved for a specific time in order to effectively implement the LTE-U technology/service. Thus, in an LTE-U cell, downlink transmission may be performed through a set of one or more consecutive subframes (DL transmission bursts) after LBT. According to the LBT case, the DL transmission burst may start with a normal subframe (rSF) or a partial subframe (pSF). The pSF may be a portion of a subframe and may include a second slot of the subframe. Further, the downlink transmission burst may end at rSF or pSF.

< method of performing LBT in uplink grant transmission only >

Hereinafter, a channel access method for performing transmission of a downlink control channel (e.g., PDCCH or EPDCCH) in consideration of uplink grant only (UL grant only) transmission, and transmission of an uplink grant and uplink traffic schedulable through the uplink grant when channel access is performed for uplink signals and uplink data transmission through an unlicensed band will be described.

In particular, the present invention collectively illustrates an LBT method performed for transmission of a downlink control channel in consideration of only uplink grant transmission and uplink traffic transmission scheduled through a corresponding uplink grant.

Referring to fig. 15, when uplink data traffic transmitted in an LAA SCell is self-carrier scheduled by a control channel transmitted in the corresponding LAA SCell, a control channel transmitting only an uplink grant may be transmitted in a PDCCH of a DL subframe, i.e., in a case where there is no PDSCH transmission in one subframe, uplink grant only transmission may be performed in the PDCCH. In this case, the PDSCH region may be invalidated OFDM symbols that it has in a subframe without transmitting any signals, and channel access from other nodes or Wi-Fi nodes may be allowed in the corresponding invalidated OFDM symbol(s) of the unlicensed carrier.

Therefore, although the base station attempts to ensure transmission of the base station by differently configuring a Maximum Channel Occupancy Time (MCOT) configuration according to a channel access priority level and LBT performed for uplink grant transmission only is also successful, it may not be possible to transmit PDSCH and scheduled PUSCH in the next subframe, as shown in fig. 15, for transmission of PDSCH and scheduled PUSCH because of transmission and interference of other nodes due to the fact that PDSCH transmission does not occur in the corresponding subframe.

In fig. 15, a case where the starting subframe of the LAA burst on the unlicensed carrier is configured as a partial subframe in which only uplink grant transmission is performed is described as an embodiment, but the present invention is not limited thereto. As another embodiment, there may be a case where the last subframe of the LAA burst is configured as a partial subframe in which only uplink grant transmission is performed. In another embodiment, even in the starting subframe of an LAA burst in an unlicensed carrier or in a subframe that is not the last subframe of the LAA burst, an OFDM symbol that is invalidated may be generated in a subframe in which UL-only grant transmission is performed, and thus, the above-described problem may occur. Hereinafter, a method for solving the above-mentioned problems will be described.

Method A)

Fig. 16 illustrates a case where an EPDCCH including only UL grant is transmitted without PDSCH transmission. Accordingly, since EPDCCH is allocated in the PDSCH region in the FDM scheme using PDSCH, even UL-only grant transmission without PDSCH can prevent occurrence of invalid OFDM symbol(s) in the PDSCH region and can prevent other nodes from channel access through LBT.

Also, as a method for performing LBT used by the UE(s) in transmitting UL traffic corresponding to a corresponding UL grant, by performing an LBT scheme performed during transmission of the UL grant or performing a single interval LBT such as 16us, 25us, 34us, or 43us (hereinafter, referred to as type 2 channel access for convenience of explanation) when transmitting UL traffic in MCOT secured in UL grant transmission, fast channel access for UL data transmission may be achieved.

Alternatively, as a method for LBT used in UE(s) when UL traffic corresponding to a UL grant is transmitted, an LBT scheme performed during transmission of the UL grant is performed, or cat-4LBT (hereinafter, referred to as type 1 channel access for convenience of explanation) is performed when UL traffic is transmitted outside MCOT obtained during transmission of the UL grant [ t1 ].

Alternatively, in this case, the following method may be considered: by the method, the base station signals whether to perform type 2 channel access to allow the user equipment to have fast channel access as LBT for UL traffic or whether to perform type 1 channel access to perform backoff. The channel access type that the base station can inform the user equipment can be transmitted through the UL grant, and the base station can inform the type 1 channel access or the type 2 channel access in the corresponding UL grant. Here, type 1 channel access refers to Cat-4LBT, and type 2 channel access refers to 25us LBT.

Method B)

As shown in fig. 17, even when a PDCCH or EPDCCH for UL-only grant transmission is transmitted in one subframe, in the next subframe in which a PDSCH is transmitted, a method of configuring LBT to be performed according to a channel access priority class of the PDSCH may be considered, independently of LBT in a subframe for UL-only grant transmission.

In this case, when LBT in a subframe in which a PDSCH is transmitted is successful, MCOT from a corresponding subframe is configured. When a UL subframe transmitting UL traffic corresponding to a previously scheduled UL grant exists in a corresponding MCOT, type 2 channel access may be performed to enable fast channel access for UL data transmission.

Alternatively, as a method for performing LBT used in the UE(s) during transmission of UL traffic corresponding to the UL grant, the method may be configured to perform an LBT scheme performed during transmission of the UL grant, or perform type 1 channel access when UL traffic is transmitted outside the MCOT obtained through LBT in a subframe in which the PDSCH is transmitted.

Alternatively, in this case, the following method may be considered: by the method, the base station signals whether to perform type 2 channel access to allow the user equipment to have fast channel access as LBT for UL traffic or whether to perform type 1 channel access to perform backoff. The channel access type that the base station can notify the terminal may be transmitted through the UL grant, and the base station may notify the type 1 channel access or the type 2 channel access in the corresponding UL grant. Here, type 1 channel access may refer to Cat-4LBT, and type 2 channel access may refer to 25us LBT.

Method C)

Fig. 18 is a diagram illustrating a case where LBT is independently performed for a subframe for transmitting only a UL grant without PDSCH transmission and a subframe(s) for performing PDSCH transmission according to an embodiment of the present invention. The presence of the invalidated OFDM symbol(s) in the PDSCH region and the channel access by other nodes through LBT can be prevented by transmitting the reservation signal. Also, due to this, the PDSCH transmitted in the next subframe may be transmitted without additional LBT in the MCOT.

As an example of a reservation signal, there may be one EPDCCH transmission common to all UEs, and as another example, a method of extending CRS port 0 and port 1 to extend transmission in OFDM symbol indices #0, #4, #5, and #7 to the remaining symbols may be considered. Further, a form of expanding and transmitting CRS ports 0 to 4 may also be considered, and a method of transmitting dummy data as a reservation signal to an RB in a specific frequency region may be considered.

Also, as a method for performing LBT used in the UE(s) when transmitting UL traffic corresponding to the UL grant, type 2 channel access may be performed when transmitting UL traffic in the MCOT secured in the transmission of the UL grant, thereby enabling fast channel access for UL data transmission.

Alternatively, as a method for performing LBT used in the UE(s) during transmission of UL traffic corresponding to the UL grant, the method may be configured to perform a scheme of LBT performed during transmission of the UL grant, or perform type 1 channel access when UL traffic is transmitted outside the MCOT obtained in UL grant transmission.

In fig. 16 to 18, a case where the starting subframe of the unlicensed carrier based LAA burst is set to a partial subframe in which only UL grant transmission is performed, but the present invention is not limited thereto. As another embodiment, there may be a case where the last subframe of the LAA burst is set as a partial subframe in which only UL grant transmission is performed. In another embodiment, even in the starting subframe of an LAA burst in an unlicensed carrier or in a subframe that is not the last subframe of the LAA burst, an OFDM symbol that is invalidated may be generated in a subframe in which UL-only grant transmission is performed, and thus, the above-described problem may occur.

Also, although fig. 15 to 18 are described with reference to the normal subframe, fig. 15 to 18 may be equally applied to the case where the starting subframe is a partial subframe (e.g., a subframe composed of OFDM symbols less than 14) and the last subframe is a partial subframe.

Hereinafter, a DL control channel (e.g., PDCCH, EPDCCH) including a UL grant and an LBT method and an LBT scheme for UL traffic transmission corresponding to the UL grant will be described in consideration of a channel access priority level of UL traffic corresponding to the UL grant during UL grant only transmission. In addition, an LBT scheme for UL traffic transmission corresponding to a UL grant when the UL grant is transmitted together with PDSCH transmission will be described.

First, when a UL grant is transmitted together with PDSCH transmission, LBT for PDCCH and EPDCCH, which are control channels through which the UL grant is transmitted, includes: channel access is performed by using the LBT parameter according to a channel access priority level (hereinafter, referred to as CAPC for convenience) of the PDSCH.

Table 1 below shows LBT parameters in terms of channel access priority classes for transmitting PDSCH as downlink transmission.

[ TABLE 1] channel Access priority classes

As an example, when the CAPC of the PDSCH is 1 or 2, since the MCOT is 2ms or 3ms, when it is assumed that the minimum time delay of the UL grant and the UL traffic transmission is 4ms, the UL traffic transmission corresponding to the UL grant is performed outside the MCOT of the downlink burst to which the UL grant is transmitted. Accordingly, LBT of UL traffic transmission corresponding to the UL grant may be configured to perform LBT according to CAPC of UL traffic to be transmitted by the user equipment. When there are multiple CAPCs of UL traffic to be transmitted instead of one CAPC, the user equipment is configured to perform type 1 channel access based on the CAPC having the lowest priority among the multiple CAPCs.

As another example, when the CAPC of the PDSCH transmitted with the UL grant is 3 or 4, since the MCOT is 8ms or 10ms, UL traffic transmission corresponding to the UL grant may be transmitted within the MCOT, but may also be transmitted outside the MCOT. Thus, when downlink transmissions and UL LBTs and UL traffic transmissions may occur within the MCOT, a single interval (e.g., 16us, 25us, 34us, 43us, or 16+9 × N, N may be a value of 1 or greater) LBT is performed, regardless of the CAPC of the UL traffic. That is, UL traffic transmission is performed through type 2 channel access. On the other hand, in case no DL transmission and UL LBT and UL traffic transmission occur within the MCOT, type 2 channel access is performed for UL transmissions that may occur within the MCOT, regardless of the CAPC of the UL traffic, but for UL traffic transmissions scheduled to be transmitted outside the MCOT, the user equipment may be configured to perform LBT according to the CAPC of the UL traffic to be transmitted by the user equipment. When there are a plurality of CAPCs of UL traffic to be transmitted by a corresponding user equipment, the corresponding user equipment may perform type 1 channel access based on a CAPC having a lowest priority among the plurality of CAPCs.

As another example, in case of setting CAPC of PDSCH transmitted with UL grant to 3 and also performing UL grant according to CAPC 3, if CAPC of UL traffic that the user equipment actually wants to transmit is set to 3 or less, UL traffic is transmitted through type 2 channel access regardless of CAPC of UL traffic. However, if the CAPC of UL traffic is 4, the user equipment may be set to perform type 1 channel access using the LBT parameter according to CAPC 4 of UL traffic to perform UL transmission regardless of whether corresponding UL traffic transmission occurs within the MCOT. Also, when the CAPC of the PDSCH transmitted with the UL grant is configured to 4 and the transmission of the UL grant is also performed according to CAPC 4, the user equipment can perform UL traffic transmission through the type 2 channel access regardless of the CAPC of the UL traffic that the user equipment actually wants to transmit.

As another example, when LBT is performed by CAPC value X of PDSCH transmitted with UL grant, UL traffic transmission through type 2 channel access may be performed for CAPC value less than or equal to X of UL traffic. In other cases, the user equipment may be configured to perform LBT in accordance with the CAPC of the UL traffic to be transmitted by the user equipment. When there are multiple CAPCs of UL traffic to be transmitted by a corresponding user device, the corresponding user device may be configured to perform type 1 channel access based on the CAPC having the lowest priority among the multiple CAPCs.

< UL LBT type switching >

Hereinafter, a method of switching the type of UL LBT when performing UL channel access will be described.

The base station informs the user equipment of the LBT type and parameters for LBT that the user equipment should perform. The base station may specify the LBT type through the UL grant and inform type 1 channel access, type 2 channel access, or no LBT as the LBT type.

Fig. 19 is a diagram illustrating a method of switching an LBT type when DL scheduling occurs between UL grant transmission and corresponding UL traffic transmission according to an embodiment of the present invention. Specifically, in fig. 19, the base station notifies the user equipment of the LBT type through the UL grant, but it is assumed that DL scheduling occurs between the UL grant transmission and the corresponding UL transmission.

Fig. 19 (a) notifies that type 1 channel access is performed for UL traffic transmission through a UL grant in a sixth subframe or a tenth subframe starting from the first DL subframe. In this case, the user equipment may perform type 1 channel access and perform UL transmission. In (a) of fig. 19, since the MCOT is set to 3ms through the first DL subframe, UL traffic transmission scheduled in the sixth or tenth subframe does not exist within the MCOT set in the DL. Thus, the base station may instruct the user equipment to perform type 1 channel access for UL transmissions.

In contrast, when UL traffic transmission exists in the MCOT set in the DL, for example, when the MCOT is 8ms from the configuration of the first DL subframe, the base station may instruct the user equipment to perform type 2 channel access by the UL grant, and the instructed user equipment may perform type 2 channel access to transmit UL traffic.

In (b) of fig. 19, under the assumption that type 1 channel access is instructed through UL grant for transmission of UL traffic configured in a sixth subframe or a tenth subframe from a first DL subframe, when DL scheduling is performed as in a fifth subframe in (b) of fig. 19 before UL traffic transmission that has been scheduled, a method may be considered in which a user equipment that has performed DL reception may change a channel access type indicated in an UL grant that the user equipment receives from the first DL subframe.

In other words, when there is UL transmission in the MCOT configured in the DL, since the base station can transmit UL traffic through the type 2 channel access, the base station can be configured to transmit UL traffic through the type 2 channel access instead of the indicated type 1 channel access. Accordingly, the base station may provide the trigger message to enable the user equipment to perform the type 2 channel access, so that the user equipment receiving the trigger message may perform the type 2 channel access to transmit the UL traffic.

However, when configuring the UL grant instructed by the base station to perform continuous multi-subframe scheduling via one UL grant as in fig. 19 (a) and 19 (b), that is, a case where the first DL subframe is configured to perform scheduling of the sixth UL subframe and the seventh UL subframe in fig. 19 (a) and 19 (b) needs to be considered. In particular, when DL traffic to be transmitted by the base station occurs and DL scheduling is performed in the 5 th subframe and MCOT is set to 2ms in DL transmission, for UEs scheduled for the sixth and seventh consecutive multiple UL subframes in the first DL subframe, UL LBT configured for UL transmission in the sixth and seventh consecutive subframes is located within the newly set MCOT (2 ms). Therefore, UL traffic transmission may be possible by switching from type 1 channel access to type 2 channel access. However, since the LBT time point of the sixth subframe is located in the MCOT of 2ms although the LBT for the seventh subframe is located outside the MCOT of 2ms, it can benefit from performing fast channel access, so that a fairness problem may occur between systems using other unlicensed bands. To improve this, according to an embodiment of the present invention, a user equipment that schedules UL transmission for a plurality of subframes in a sixth subframe may consider a method of performing type 1 channel access for UL transmission for a seventh subframe.

On the other hand, when the length of the entire UL burst (i.e., the sixth and seventh subframes) is not included in the newly set DL MCOT, in (b) of fig. 19, a method of performing a channel access type configurable by a previous UL grant (i.e., type 1 channel access configurable by a UL grant from the first DL subframe) may be considered.

Although the UL bursts in the sixth and seventh subframes are described with reference to fig. 19, fig. 19 may be equally applied to the UL bursts in the tenth and eleventh subframes.

Fig. 20 is a diagram illustrating another example of switching a channel access type according to another embodiment of the present invention when DL scheduling occurs between UL grant transmission and corresponding UL traffic transmission. In the same manner, in particular, in fig. 20, the base station notifies the user equipment of the channel access type through the UL grant, but assumes that DL scheduling occurs between the UL grant transmission and the corresponding UL transmission. Further, in fig. 20, it is assumed that a channel access type for UL burst is notified when a plurality of subframes are scheduled, and the user equipment performs corresponding LBT.

In (a) of fig. 20, the base station schedules a tenth UL subframe and an eleventh UL subframe in the first, second or third DL subframe, i.e., through a UL grant on the previous DL burst, and instructs to perform type 1 channel access and transmit UL traffic as an associated channel access type.

Incidentally, as shown in (b) of fig. 20, when DL scheduling (e.g., eighth and ninth subframes) occurs between UL grant transmission and corresponding UL traffic transmission, UL traffic transmission exists in the MCOT of the DL when the MCOT of the DL burst includes tenth and eleventh UL subframes as UL bursts. Accordingly, the channel access type for the tenth UL subframe and the eleventh UL subframe is switched to the type 2 channel access to transmit the UL traffic.

On the other hand, as shown in (c) of fig. 20, if the MCOT of a DL burst occurring between a UL grant transmission and a corresponding UL traffic transmission does not include a UL burst (i.e., a tenth UL subframe and an eleventh UL subframe), it is allowed to perform type 2 channel access only for a UL subframe included in the MCOT among the UL bursts, and if not, to transmit UL traffic by performing type 1 channel access for the eleventh subframe.

Also, as shown in (d) of fig. 20, when the length of the entire UL burst scheduling a plurality of subframes is not included in the newly formed MCOT, UL burst LBT is performed by using a channel access type previously indicated by the base station through UL grant to transmit UL traffic.

Finally, in (e) of fig. 20, when DL scheduling (eighth and ninth subframes) occurs between UL grant transmission and corresponding UL traffic transmission, if the MCOT of a DL burst does not include any part of the UL burst, UL burst LBT is performed to transmit UL traffic by using a channel access type previously indicated by the base station through UL grant.

Fig. 21 is a diagram illustrating another example of switching a channel access type when DL scheduling occurs between UL grant transmission and corresponding UL traffic transmission according to an embodiment of the present invention. In particular, in fig. 21, the base station notifies the user equipment of the channel access type through the UL grant, but it is assumed that DL scheduling occurs between the UL grant transmission and the corresponding UL transmission. Also, in fig. 21, it is assumed that a channel access type for each UL subframe constituting a UL burst is notified when a plurality of subframes or a single subframe is scheduled, and the user equipment performs a corresponding LBT.

In (a) of fig. 21, the base station schedules a tenth UL subframe and an eleventh UL subframe in the first, second or third DL subframe, i.e., through a UL grant on the previous DL burst, and instructs to perform type 1 channel access and transmit UL traffic for each UL subframe.

However, as shown in (b) of fig. 21, if the MCOT of the DL burst occurring between the UL grant transmission and the corresponding UL traffic transmission does not include the UL burst (i.e., the tenth UL subframe and the eleventh UL subframe), the UL traffic is transmitted by allowing the type-2 channel access to the UL subframe included in the MCOT among the UL bursts and not performing the type-1 channel access to the eleventh subframe not included in the MCOT.

Also, as shown in (c) of fig. 21, when the length of the entire UL burst scheduling a plurality of subframes is not included in the newly formed MCOT, LBT is performed to transmit UL traffic by using a channel access type previously indicated by the base station through the UL grant.

An implicit or explicit signaling method for switching the LBT type described through fig. 19 to 21 from the base station may be considered, and as implicit signaling, by determining whether there is transmission of a UL burst in the MCOT newly formed by receiving the first DL subframe on the DL burst, it is possible to change a channel access type for UL transmission and perform LBT to transmit UL traffic.

Alternatively, as the explicit signaling, if DL scheduling occurs between UL grant transmission and corresponding UL traffic transmission, the base station may transmit signaling for changing a channel access type to the user equipment, and the user equipment may change the channel access type by receiving the corresponding signaling to transmit the UL traffic. Alternatively, the base station notifies the user equipment of the MCOT of each DL burst, and if the UL burst is configured to be completed within the MCOT configured by the base station, the user equipment may change a channel access type to perform LBT through type 2 channel access and transmit UL traffic.

< UL burst indication >

Meanwhile, if the base station schedules UL transmission for a plurality of user equipments, the base station may know whether an UL subframe to be scheduled is a last UL subframe for a UE in a cell when transmitting an UL grant. Therefore, it is preferable that the base station signals whether the subframe to be scheduled for the UE is the last subframe. As a signaling method, when transmitting the UL grant, there may be a notification method by a DL common control signal for DL or a notification method by a UL common control signal.

As an example of the common control signal described above, a PDCCH having DCI scrambled by CC-RNTI may be represented. The base station may inform the UE of the last subframe of the UL subframes through a common control signal. If the scheduled UL subframe(s) are all included before the last subframe in the cell indicated by the common control signal, the user equipment may perform type 2 channel access to perform UL transmission in the scheduled UL subframe(s), regardless of the channel access type indicated by the base station for the scheduled UL subframe(s).

On the other hand, when the scheduled UL subframe(s) includes only partially or not all before the last subframe indicated by the common control signal in the cell, the user equipment may perform channel access according to the channel access type indicated for the UL subframe(s) scheduled by the base station and perform UL transmission in the scheduled UL subframe(s).

< method of performing LBT for consecutive UL transmissions after DL transmission >

Hereinafter, a UL channel access method for continuous UL transmission after DL transmission in an LAA cell will be described.

As in fig. 22, even if the base station transmits a UL grant to the user equipment in subframe # n and schedules UL transmission in subframe # (n +4), any user equipment can recognize through PDCCH/EPDCCH that the PDSCH for the user equipment itself is included in DL transmission from the base station in subframe # (n +3) or recognize its DL scheduling through PDCCH/EPDCCH and decoding PDSCH success.

In this case, DL reception is completed, and UL traffic transmission of the user equipment without UL LBT or only type 2 channel access may be performed immediately after a certain interval (e.g., 16us, 20us, or 25us, or any other value) from the time when DL reception is completed. Since LBT is performed once in DL during UL grant transmission, the user equipment may not additionally perform UL LBT for UL transmission expected by the UL grant, or perform a simple LBT operation without backoff to transmit UL traffic.

Here, when UL traffic is transmitted after a certain interval, transmission after a certain period may be considered regardless of a subframe boundary, or transmission may be performed corresponding to an OFDM symbol (or SC-FDMA symbol) boundary. Alternatively, there may be a method of transmitting UL traffic corresponding to UL subframe boundaries. However, when a certain interval is set, it may be preferable to consider the switching time from DL to UL.

Fig. 23 shows an example in which a user equipment transmits a data channel to a base station according to another embodiment of the present invention.

Referring to fig. 23, when UL transmission is scheduled after a DL subframe in the same carrier, a user equipment may start UL transmission according to a channel access procedure that is not based on a backoff procedure. In particular, the user equipment may perform type 2 channel access and start UL transmission based on whether the channel is idle during a single sensing interval.

In particular, the user equipment senses whether the channel is idle during a single sensing interval. If the channel is idle, the user equipment may start UL transmission through the corresponding channel. At this time, the single sensing interval may represent a minimum time interval of idle time intervals required for the user equipment to access the channel. At this time, the user equipment may determine whether a corresponding channel is idle through a Clear Channel Assessment (CCA) operation. In addition, the user equipment may start UL transmission at a subframe boundary. At this time, the user equipment may sense whether a channel corresponding to UL transmission is idle during a single sensing interval (e.g., 25us interval), and may start UL transmission when the corresponding channel is idle. At this time, the specific operation of the user equipment may be the same as the method of transmitting UL by performing the above-described type 2 channel access.

Fig. 24 illustrates a configuration of a user equipment and a base station according to an embodiment of the present invention. In the embodiments of the present invention, the user equipment can be realized by various types of wireless communication apparatuses or computing apparatuses that are guaranteed to be portable and have mobility. The user equipment may be referred to as a Station (STA), a Mobile Subscriber (MS), etc. In an embodiment of the present invention, a base station may control and manage cells (e.g., macro cells, femto cells, pico cells, etc.) corresponding to a service area, and perform functions such as transmitting signals, designating channels, monitoring channels, self-diagnosis, relaying. A base station may be referred to as an evolved node b (enb), Access Point (AP), etc.

Referring to fig. 24, the user device 100 may include a processor 110, a communication module 120, a memory 130, a user interface unit 140, and a display unit 150.

The processor 110 may execute various commands or programs according to the present invention and process data in the user equipment 100. Further, the processor 100 may control all operations of the respective units of the user equipment 100 and control data transmission/reception between the units. For example, the processor 110 may receive a DL signal in an LTE-U cell in an LAA environment, and may transmit a HARQ-ACK response for the DL signal to a base station.

The communication module 120 may be an integrated module that performs mobile communication by using a mobile communication network and wireless LAN access by using a wireless LAN. To this end, the communication module 120 may include a plurality of network interface cards, such as cellular

communication interface cards

121 and 122 and an internal or external type wireless LAN interface card 123. In fig. 24, the communication module 120 is illustrated as an integrated module, but a corresponding network interface card may be independently provided according to a circuit configuration or a purpose different from that of fig. 24.

The cellular communication interface card 121 transmits/receives a radio signal to/from at least one of the base station 200, an external device, and a server by using a mobile communication network, and provides a cellular communication service at the first frequency band based on a command of the processor 110. The cellular communication interface card 121 may include at least one NIC module using an LTE licensed frequency band. The cellular communication interface card 122 transmits/receives a radio signal to/from at least one of the base station 200, an external device, and a server by using a mobile communication network, and provides a cellular communication service at the second frequency band based on a command of the processor 110. The cellular communication interface card 122 may include at least one NIC module that uses an LTE unlicensed frequency band. For example, the LTE unlicensed band may be a 2.4GHz or 5GHz band.

The wireless LAN interface card 123 transmits/receives a radio signal to/from at least one of the base station 200, an external device, and a server through wireless LAN access, and provides a wireless LAN service at the second frequency band based on a command of the processor 110. The wireless LAN interface card 123 may include at least one NIC module using a wireless LAN frequency band. For example, the wireless LAN frequency band may be an unlicensed radio band, such as a 2.4GHz or 5GHz band.

The memory 130 stores a control program and various result data used in the user equipment 100. The control program may include a program required for the user equipment 100 to perform wireless communication with at least one of the base station 200, an external device, and a server. The user interface 140 includes various types of input/output devices provided in the user apparatus 100. The display unit 150 outputs various images on a display screen.

Further, the base station 200 according to an exemplary embodiment of the present invention may include a processor 210, a communication module 220, and a memory 230.

The processor 210 can execute various commands or programs according to the present invention and process data in the base station 200. Further, the processor 210 may control all operations of the respective units of the base station 200 and control data transmission/reception between the units. For example, the processor 210 may perform downlink transmission. Specifically, processor 210 may perform downlink transmission, HARQ-ACK feedback set checking, CWS adjustment, and the like according to cases 1, 2-2.

The communication module 220 may be an integrated module that performs mobile communication by using a mobile communication network and wireless LAN access by using a wireless LAN, such as the communication module 120 of the user equipment 100. To this end, the communication module 120 may include a plurality of network interface cards, such as cellular

communication interface cards

221 and 222 and an internal or external type wireless LAN interface card 223. In fig. 18, the communication module 220 is illustrated as an integrated module, but a corresponding network interface card may be independently provided according to a circuit configuration or a purpose different from that of fig. 18.

The cellular communication interface card 221 transmits/receives a radio signal to/from at least one of the user equipment 100, an external device, and a server by using a mobile communication network, and provides a cellular communication service at the first frequency band based on a command of the processor 210. The cellular communication interface card 221 may include at least one NIC module using an LTE licensed frequency band. The cellular communication interface card 222 transmits/receives a radio signal to/from at least one of the user equipment 100, an external device, and a server by using a mobile communication network, and provides a cellular communication service at the second frequency band based on a command of the processor 210. The cellular communication interface card 222 may include at least one NIC module that uses an LTE unlicensed frequency band. The LTE unlicensed band may be a 2.4GHz or 5GHz band.

The wireless LAN interface card 223 transmits/receives a radio signal to/from at least one of the user equipment 100, an external device, and a server through the wireless LAN access, and provides a wireless LAN service at the second frequency band based on a command of the processor 210. The wireless LAN interface card 223 may include at least one NIC module using a wireless LAN frequency band. For example, the wireless LAN frequency band may be an unlicensed radio band, such as a 2.4GHz or 5GHz band.

In fig. 24, blocks of the user equipment and the base station are logically divided and illustrate elements of the apparatus. The elements of the device may be mounted as one chip or as a plurality of chips, depending on the design of the device. Further, some components of the user device 100 (that is, the user interface 140 and the display unit 150) may be selectively provided in the user device 100. Further, some components of the base station 200 (that is, the wireless LAN interface 223 and the like) may be selectively provided in the base station 200. The user interface 140 and the display unit 150 may also be provided in the base station 200, if desired.

The method and system of the present invention have been described in terms of specific embodiments, but some or all of the elements and operations of the invention may be implemented using a computer system having a general-purpose hardware architecture.

The present invention has been described for illustrative purposes, and it will be appreciated by those skilled in the art that the present invention may be easily modified into other detailed forms without changing the technical spirit or essential features of the present invention. The foregoing exemplary embodiments are, therefore, to be considered in all respects illustrative rather than restrictive. For example, various components described as a single type can be implemented as distributed components, and similarly, components described as distributed components can also be implemented in combination.

The scope of the present invention is indicated by the claims to be described below (rather than by the detailed description), but should be construed to be within the meaning and scope of the claims and all changes or modifications derived from equivalents thereof.

Industrial applicability

The present invention is applicable to various communication apparatuses (e.g., a station using unlicensed band communication, a station using cellular communication, a base station, etc.) used in a wireless communication system.

Claims

1. A method for performing uplink transmission to a base station through an unlicensed cell by a user equipment in a wireless communication system, the method comprising:

receiving an uplink grant from the base station scheduling the uplink transmission in at least one subframe; and

performing the uplink transmission in the at least one subframe using at least one of a first type channel access based on channel sensing with random backoff using variable sized CWs (contention windows) before data transmission, wherein a maximum value of a CW and a minimum value of a CW are determined according to a channel access priority level of the uplink transmission or a second type channel access based on channel sensing with a single interval before data transmission,

wherein the uplink transmission is performed using the second type of channel access when all of the uplink transmissions in the at least one subframe are included in a predetermined interval determined based on downlink transmissions from the base station through the unlicensed cell.

2. The method of claim 1, wherein the uplink grant indicates a channel access type to be used in the uplink transmission among the first type of channel access or the second type of channel access.

3. The method of claim 1, wherein the uplink transmission is performed using a channel access type indicated in the uplink grant when the uplink transmission in the at least one subframe is not included in the predetermined interval or only a portion of the uplink transmission in the at least one subframe is included in the predetermined interval.

4. The method of claim 1, wherein the predetermined interval is determined based on a maximum channel occupancy time set by the downlink transmission.

5. The method of claim 1, wherein the information regarding whether the at least one subframe is a last subframe for the uplink transmission is received through a common control channel.

6. The method of claim 1, wherein the uplink transmission is performed using the second type of channel access when the uplink transmission is performed in a next subframe of the downlink transmission by the unlicensed cell.

7. A user equipment in a wireless communication system, the user equipment comprising:

a wireless communication module; and

a processor configured to receive, by the wireless communication module, an uplink grant scheduling the uplink transmission in at least one subframe from the base station, and perform, by the wireless communication module, the uplink transmission in the at least one subframe using at least one of a first type channel access based on channel sensing with random backoff using variable-sized CW (contention window) before data transmission or a second type channel access determined according to a channel access priority level of the uplink transmission, wherein the second type channel access is based on channel sensing with a single interval before data transmission,

wherein the processor performs the uplink transmission using the second type of channel access when all of the uplink transmissions in the at least one subframe are included in a predetermined interval determined based on downlink transmissions from the base station through the unlicensed cell.

8. The user equipment of claim 7, wherein the uplink grant indicates a channel access type to be used in the uplink transmission among the first type of channel access or the second type of channel access.

9. The user equipment of claim 7, wherein, when the uplink transmission in the at least one subframe is not included in the predetermined interval or only a portion of the uplink transmission in the at least one subframe is included in the predetermined interval, the processor is configured to perform the uplink transmission using a channel access type indicated in the uplink grant.

10. The user equipment of claim 7, wherein the predetermined interval is determined based on a maximum channel occupancy time set by the downlink transmission.

11. The user equipment of claim 7, wherein the information regarding whether the at least one subframe is a last subframe for the uplink transmission is received through a common control channel.

12. The user equipment of claim 7, wherein when the uplink transmission is performed in a next subframe of the downlink transmission through the unlicensed cell, the processor is configured to perform the uplink transmission using the second type of channel access.

13. A method for a base station to receive uplink transmissions from user equipment through an unlicensed cell in a wireless communication system, the method comprising:

transmitting an uplink grant to the user equipment, the uplink grant scheduling transmission of the uplink transmission in at least one subframe and indicating a channel access type to be used when the user equipment transmits the uplink transmission among a first type channel access based on channel sensing with random backoff using variable-sized CWs (contention windows) before data transmission or a second type channel access, wherein a maximum value of a CW and a minimum value of a CW are determined according to a channel access priority level, wherein the second type channel access is based on channel sensing with a single interval before data transmission; and

receiving the uplink transmission in the at least one subframe,

wherein the method further comprises: transmitting common downlink control information indicating that the second type of channel access is performed in the uplink transmission when all of the uplink transmissions in the at least one subframe are included in a predetermined interval determined based on downlink transmissions through the unlicensed cell.

14. The method of claim 13, wherein the uplink grant indicates the first type of channel access when the uplink transmission in the at least one subframe is not included in the predetermined interval or only a portion of the uplink transmission of the at least one subframe is included in the predetermined interval.

15. The method of claim 13, wherein the predetermined interval is determined based on a maximum channel occupancy time set by the downlink transmission.

16. The method of claim 13, wherein the common downlink control information includes information regarding whether the at least one subframe is a last subframe for the uplink transmission.

17. A base station in a wireless communication system, the base station comprising:

a wireless communication module; and

a processor configured to transmit, by the wireless communication module, to a user equipment, schedule uplink transmission through an unlicensed cell in at least one subframe and indicate an uplink grant of a channel access type to be used when the user equipment transmits the uplink transmission among a first type channel access based on channel sensing with random backoff using variable-sized CWs (contention windows) before data transmission or a second type channel access, wherein a maximum value of a CW and a minimum value of a CW are determined according to a channel access priority class, wherein the second type channel access is based on channel sensing with a single interval before data transmission, and receive, by the wireless communication module, the uplink transmission from the user equipment in the at least one subframe,

wherein, when all of the uplink transmissions in the at least one subframe are included in a predetermined interval determined based on downlink transmissions through the unlicensed cell, the processor is configured to transmit common downlink control information indicating that the second type of channel access is performed in the uplink transmissions.

18. The base station of claim 17, wherein the uplink grant indicates the first type of channel access when the uplink transmission in the at least one subframe is not included in the predetermined interval or only a portion of the uplink transmission of the at least one subframe is included in the predetermined interval.

19. The base station of claim 17, wherein the predetermined interval is determined based on a maximum channel occupancy time set by the downlink transmission.

20. The base station of claim 17, wherein the common downlink control information includes information regarding whether the at least one subframe is a last subframe for the uplink transmission.